Magnetic filters, which are designed to remove magnetic particles entrained in system water, are now commonly installed in central heating systems. Central heating systems include a main circuit which carries system water around the system. The system water often contains various chemicals, for example inhibitors, as well as magnetic and non-magnetic dirt which is picked up from radiators and other devices in the circuit.
All magnetic filters include a separation chamber, through which system water flows, and a magnet which is designed to attract particles entrained in the system water, as the water flows through the separation chamber. The particles are then typically retained within the chamber until the magnetic filter is serviced and the retained particles are removed and disposed of.
Various different types of filter are known in the art. For example, the Applicant's granted British Patent GB2486172 discloses a filter which includes a sealed canister through which system water flows, and a sleeved magnet inside the canister. When the filter needs to be cleaned, the filter must be disconnected from the heating circuit and the canister must then be opened to remove the sleeve and magnet. Once the sleeve has been removed from the canister, the magnet can be removed from the sleeve allowing magnetic particles to be easily removed and disposed of.
Disconnecting the filter from the heating circuit is a necessary step before opening the canister, because otherwise system water will flow out of the system when the canister is opened. Even with the filter disconnected, some leakage or spillage is not unlikely when opening the sealed canister, removing and replacing the magnet. Also, repeatedly opening the canister makes damage to the seal more likely.
Some other types of filter provide a magnet outside the sealed canister. For example, the filter disclosed in WO2013077729 (SPIRO ENTERPRISES) includes a magnet which can be detachably positioned around the outside of the canister. In this type of filter, flushing of magnetic particles can be achieved by disconnecting the filter from the heating circuit (by closing valves), removing the magnet, and opening a drain valve. The water contained within the canister will then drain out (for example, into a bucket) and the magnetic particles—which are no longer being retained by the magnet—will drain away as well. Optionally, one of the valves connecting the filter to the heating circuit may be opened briefly, causing pressurised system water to rush out of the system via the filter, cleaning out any magnetic particles which are still inside.
The advantage of this type of filter is that it can be cleaned without opening the sealed canister. Only a drain valve has to be opened. This provides a more controlled cleaning process, which is less likely to result in spillage. Also, the seal on the canister is less likely to fail, since the canister never needs to be opened for servicing. Indeed, it may be possible to manufacture the canister integrally as a single sealed unit.
Unfortunately, this type of filter is generally less effective at removing magnetic particles, because the strength of the magnet is attenuated by the thickness of the wall of the canister.
It is an object of the invention to reduce or substantially obviate the above mentioned problems.